[size=small]One board are ready and working. Everything work perfect - LED switched color at 21.8V as expected, charger charge.[/size][size=small][/size]
[size=small]With Lm4562 and gain 2 sound is really powerful and clean, like with my external regulated 24V PS, maybe little cleaner and more controlled bass (probably just placebo [/size]
Amp perform good, like any CMoy, depending chip used
DC offset is very low, with FET input opamp like OPA2134 - less than 1 mV, with bipolar input like LM4562 - 2-4 mV
Main improvement over simpler CMoy is increased headroom, because of high power voltage. This is especially good for higher impedance phones.
PCB are available, if someone are interested, 20 Euro including shipping.
Yes, bottom part is voltage multiplier and charger, voltage splitter is TLE2426, LM4562 is dual opamp for both channels, on schematic one channel shown, second channel is similar. Virtual ground/rail splitter is one for whole amp, as always.
And here you can see most important difference from first prototype - battery voltage indicator in action
[size=small]Upper image - battery voltage in good condition.[/size][size=small][/size]
[size=small]Lower image - battery voltage too low, requires charging. Actually LED's color is red here, just bad camera.[/size]
I make small change in schematic. 75 ohm resistor near LM317 is changed to 50 ohm or even 46 ohm, for increasing charging current from 16mA to 25-27mA.
In the beginning I just copy/paste 75 ohm resistor from some older well known designs like amb's m3 or Tangent's PIMETA. In real world 16mA is too slow for today's 250-280mAh batteryes, overnight charging not charging battery at max.
So, I increase current closer to C/10.
This information will be usable for anyone who use amp with 9V batteries and built in charger, not depend - one battery, 2 or 3 in series.